Brake mechanism and magnet system therefor



BRAKE MECHANISM AND MAGNET SYSTEM THEREFOR BY www l A TTORNE Dec.1,1925. 1,563,544

W. S. ATKINSON BRAKE MECHANISM AND MAGNET SYSTEM THEREFOR Filed D60, 14,1925 2 Sheets-Sheet 2 INVENTOR. 5

Illlll' 4 ATToRNEY.

Patented Dec. 1, 1925.

UNITED t STA'l as PATENT oFFlcE.

WILLARD S. ATKINSON, OF ASHLAND, JERSEY, ASSIGNOB, '10 ATLANTIC ELE-VATOR COMPANY, OF PHILADELPHIA, PENNSYLVANIA, A CORPORATION F PENN-SYLVANIA. v

BRAKE MECHANISM AND MAGNET SYSTEM THEREFOR.

' Anpiieation me'drecember 14, 192s. serieu No. 680,610.

To all 'whom it may concern:

Be it known that I, WILLARD S. ATKINSON, a citizen of the United States,residing in Ashland, county of Camden, State of New Jersey, haveinvented certain new and useful Improvements in Brake Mechanism andMagnet Systems Therefor, of which the following is a specification.

My invention relates to brake mechanisms, more particularly thoseutilized in elevator systems, and relates also to a magnet system forcontrolling the brake mechanism.

ln accordance with my invention, the brake mechanism is controlled by amagnet system comprising two or more electromagnets energizedindependently of each other from a two or more phase alternating currentcircuit to effect uniformity or consistency of action of the magnetsystem upon the brake mechanism, to avoid chattering,

and to ensure approximately constant brakecontrolling force throughout aconsiderable range of movement ofthe movable magnet elements.

Further in accordance with mv invention, there is provided in analternating or fluctuating current magnet, in which relatively movablemembers of the magnetic. circuit come into engagement or contact witheach other, a restricted area of engagement or Contact, materially lessthan either of the areas at the adjacent ends or portions of theco-acting members and materially greater than a point.

My invention resides in features hereinafter described and claimed.

For an illustration of one of the various forms my invention may take,reference is l l to be had to the accompanying drawings, in

Fig. 6 is a bottom plan View of one of the magnet core members.

Fig. 7 is a v.fragmentary view of the movable magnet cores and adiagrammatic view of the circuit connections of the magnet windings.

Referring to the drawing, 1 is a base or support of any suitablecharacter, for example, for an electric motor which operates thecable-winding mechanism of an elevator or elevator system. 2 indicatesthe cylindrical brake drum or pulley, generally secured upon thearmature or rotor shaft of the motor. Pivoted to the base 1 at 3, 3 arethe levers 4, 4, to each of which is pivoted at 5 a brake shoe 6,preferably provided with a brake lining 7 engaging the brake drum 2..

Each brake shoe 6 may be adjusted as to its angular position withrespect to its lever 4 by the adjustable set screws 8. Carried by thebase 1 is the bracket 9, to which there is pivoted at 10 the brakecontrol or operating lever 11, which has pivoted thereto at 12 thepiston rod 13 carrying at its end the plunger or piston 14 movablewithin the cylinder 15 pivoted at 16 to a bracket 17. The piston 14 andcylinder constitute a dash pot which retards movement of the lever 11,and. all parts attached thereto, in either direction or in bothdirections.

Each of the lever arms 4 is provided with a'recess or pocket 18. inwhich is disposed the helical spring 19 engaging at its opposite endthev floating abutment 20. Both abutments 20 are adjustably secured uponthe floating rod or abutment-connecting member 21 by the nuts 22threaded and adjustable upon the rod 21 and locked in adjusted positionby the lock nuts 23. Pivoted to each of the lever arms 4 at 24 is alinkor rod 25, the rods 25 being pivoted, respectively, at 26 and 27 tothe lever l1 on opposite sides of its pivot 10.

With the parts in the position indicated in Fig. l, the brake is set,since the springs 19 are thrusting inwardly upon the lever arms 4,thereby thrusting the brake shoes in effect counterclockwise rotation ofthe The member 51 and the parts attached lever 11 about its pivot 10,the links 25, 25 thrust against the inner ends of the arms 4, forcingboth outwardly away from the drum 2, thereby lifting the brake shoesfrom engagement with the drum. And upon release of the force so exertedupon the lever 11, the springs 19, previously under compression,

expand, thrusting the upper ends of the levers 4 inwardly, causing thebrake shoes to re-engage the drum 2.

Pivoted to the lever 11 at 28 and 29 are the rods and 31, pivoted,respectively, at 32 and 33 to the movable core structures 34 and 35,respectively, of two independent single phase alternating currentmagnets whose windings 36 and 37 are connected, respectively, todifferent phases of a two-phase alternating currentsupply system ofwhich the conductors 38, 38 supply current of one phase while theconductors 39, 39 supply the current of the second phase, generally inguadrature with or dephased ninety degrees rom the current traversingthe conductors 38.

inasmuch as the independent electro-magnets are or may be similar toeach other, a description of the construction of onewill sufiice forboth.

Referring to Figs. 2 to 5 inclusive, the

, movable core structure is, by Way of example, and. preferably,U-shaped, comprising the plungers or limbs 40, 40 and the yoke 41. Thecore structure proper comprises superposed laminas of iron, mild steelor other suitable core material. The stack of superposed U-shapedlaminae 42 is confined between the cheek members 43, secured to eachother by the rivets or equivalent members 44, the members 43 more orless completely enclosing the laminae 42, as indicated in section inFig. 5. The cheek members 43 carry at their upper ends thepivot-supporting lugs 45, whereby pivotal connection is made with theaforesaid rod 30.

The limbs 40 are disposed within the magnet windings or coils '36,disposed between the plates 46 and 47, spaced from each other by thespacer tubes or bushings 48, through which extend the bolts 49, whichextend also through the flange 50 at the upper end of the cup-shapedmember 51, the members 46 and 47 being held at fixed distance from eachother, and between them are confined the coils 36, 36; and there issimultaneously held in fixed position to the magnet coils the member 51,in which lies, unrestrained, the

relatively fixed member 52 of the magnetic circuit. The fixed member orkeeper 52 comprises a. bundle or stack of laminae 53 held between cheekmembers 54, secured to each other by rivets or equivalent members 55.The member 52has 'a longitudinal extent sufficient to bridge the freeends of the movable core structure. as indicated in Fig. 2.

thereto are pivoted at 56 to the bracket 57, which may be attached tothe bracket 9 or base 1, or any other suitable fixed support.

As indicated in Figs. 2, 3 and 6, the ends of the limbs 40 are notstraight or flat, but are rounded or tapered in virtue of the fact thatthe end-surfaces are those of spheres, cones, pyramids or equivalent.Each of the limbs 40 is flattened, as indicated at 58, whereby the areaof engagement or contact between the limbs 42 and the keeper or fixedmember 52 of the magnetic circuit is materially greater than a point andmaterially less than the areas, of the ends of the limbs 42.

In the example of my invention illustrated, the movable core structuremay rock or pivot upon the pivot 32, which is normal to the pivots 28and 56 and which is also normal to the longitudinal extent of the yoke41 of the U-shaped movable corel `While in Fig. 7 the windings 36 and 37are shown permanently connected to the supply conductors 38 and 39, itwill be understood that .switching mechanism will intervene be# tweenthe conductors and these windings for closmg and opening their circuitsat desired times. In an elevator syste-m this switchingl mechanism isunder the control of a control 'lever or cable manipulated by theoperator upon the car.4

The operation is as follows:

Vth the parts in the position indicated in Fig. 1, the movable corestructuresare in their elevated positions with the brake shoes 6 set inengagement with the brake drum 2 by the springs19. Upon energization ofthe windings 36 and 37, by closing the aforesaid switching mechanism,the cores will be pulled downwardly due to the attractive effect causedby the current traversing the windings and existing between the movablecore structure and the relatively fixed keeper or lstationar'y member 52of the magnetic circuit, the attraction being continued until thc limbs40 engage the keeper or member 52. The fully attracted position isindicated in Figs. I2 and 3, and in attaining that position the magneticattractions of the two magnets have overcome the opposition of springs19, by tilting the lever 11 in counterclockwise direction, therebyliftingthebrake shoes from the drum 2. Upon rupture of the circuit ofthe windings 36 and 37, the springs 19 restore the parts to the positionindicated in Fig. 1. l

By utilization of independent single phase magnets energized fromdifferent phases of -a polyphase system, the pull upon the lever 11isnever zero during energization of the windings 36 and 37, because theenergizing currents are in quadrature with each other.

My magnet system comprising independent single phase magnets connectedin different phases of a polyphase system vhas practical advantages notheretofore avail# able either with one single phase magnet or apolyphase magnet comprising a plurality of magnet windings connected indifferent phases of a polyphase circuit and co-acting with a commonmagnetic circuit or parts of magnetic circuits having a common fluxpath.

In the case ofemployment of one single phase magnet, even when providedwith a shading coil or equivalent, the pull is periodically zero orsubstantially zero, and in .the intervals between zero or minimum pullsthe attraction rises to a maximum and again falls to zero or minimum. Inpractice the result has Men that when -the movable core structure hasreached the limit of its movement and is in engagement or contact withthe stationary member of the magnetic circuit, there results chattering,and humming, the chattering being due to the fact that thebrake-applying spring is under its maximum tension, therefore opposingits greatest force to the magnetic attraction, and since the magneticattraction passes through zero magnitude the spring begins to return thebrake towards drum-engaging position, but soon thereafter the magneticattraction reaches suiiicient magnitude to again compress the spring.This cycle of operations is repeated, causing chattering.

Nevertheless, a single phase electro-magnet has advantages over apolyphase magnet in that with the movable core structure retracted or atthe uppermost limit of its movement the inductance of the magnet windingis small or at its minimum, and the magnetizing current is at itsmaximum. The resultant magnetic attraction draws the core towards thefixed member of the magnetic circuit, andas the core proceeds into themagnet winding the inductance increases and the magnetizing currentdecreases, but because of shortened air gap in the magnetic circuit theattractive force or effective pull exerted by the magnet remains roughlythe same or constant throughout .the travel 0fthe core. 0n the contrary,in a polyphase magnet, because the magnet windings are mutuallyinductively related,`they inductively affect each other, through theircommon magnetic circuit, with the result that with the changes ininductance, and therefore of magnetizing currents traversing thepolyphase windings, there are set up in the different phase circuitsreactions, causing inconsistent and. erratic action of the polyphasemagnet as a whole, and there isan appreciably greater departure ofmagnitude of the lmagnetic pull from substantial or approximateconstancy throughout the range of movement of the core.

Furthermore, due to the reactions between the windings of the polyphasemagnet, or due Atact.

to other causes, the polyphase magnet 'itself is frequently subject tochattering.

Nevertheless, the polyphase magnet has the advantage that itseifectivepull is never zero, but the pull exerted upon the brake.- lifting leveris due t0 the interaction of dephased magnetizing currents, and, thepull which fiuctuates between finite values greater than zerocorresponds with a magnetic attraction varying in magnitude betweenfinite limits other than zero, while in accordance with my invention,employing the independent single phase magnets, each effects its ownmagnetic pull upon the brakecontrolling mechanism, and the pullseffected' by the magnet windings are for the first time combinedmechanically external to thev approximately 4constant attraction.

Chattering is avoided as aforesaid by employing on at least one, andeither one, of the relatively movable magnetic elements a surface whichis curved, tapered or the like, with a restricted area of engagement orcon- Vhere the movable core and fixed magnetic member engage over alarge sur face, the residual magnetism is often of sumcient intensity tohold the parts attracted in engagement With each other even after theexciting current is discontinued, preventing entirely or at leastpreventing prompt resetting of the brake shoesby the spring mechanism.On the other hand, where the area of engagement or contact between therelatively movable magnetic elements is greatly restricted, as in thecase of a 'point or extremely small area, chattering occurs because theresidual magnetism acting through the greatly restricted area is unableto overcome the opposing force of the spring until the current hasrisento a value substantially greater than zero. However, in accordancewith my invention, wherethe area is much greater than that of a.y pointor the like and much less than the arca of either of the kopposingfaces, the residual magnetism operative through the restricted areaofcontact is sufficiently small to permit the springs with certainty toreset the brakes upon discontinuance of current; and yet the area orengagement or contact'is sufficiently large that the residual magnetismacting therethrough is sufficient to hold the core structure in fullyattracted position over the instant of zero or minimum current in theinagnet winding. In other words, the area of engagement or contact is acompromise between ull surface contact and minute surface contact, withthe result that both undesired effects, failure to release andchattering, are overcome.

My independent single phase magnet structures independently operatingupon the brake-control mechanism have been in practical and commercialuse, where they effect the advantages of both the single phase andpolyphase magnets and avoid or overcome disadvantages ot both.

As stated, each of the keepers or relatively fixed elements 52 of themagnetic circuit simply lies free in the 'member 51, so that it mayslightly move. if necessary, to come into contact with both poles of themovable core structure. i

Furthermore, to cause both movable core structures to come into contactat both poles with the members 52 at the same time, either or both ofthe rods 30 and 31 may be adjusted as to effective length, as by itsthreading into the member 30a or 3l, the rods being provided with thelock nuts 30b and 31".

The flat surface 58 may be of any suitable shape, as circular,elliptical, polygonal, etc.,

but, as indicated in Fig. 6, may be a square whose diameter may be ofthe order of onelialf inch when the diameter of the movable corestructure or plunger 1s of the order of two inches, this relation beinggiven, however, merely by way of example, and is not by way oflimitation of my invention.

What I claim is: l. The combination with an elevator brake mechanismcomprising a brake drum, braking means co-acting therewith, and acontrol lever, of a plurality of single phase electro-magnets whosemagnetic-circuits are substantially independent and each comprisingrelatively movable core elements and a' Winding, means for connectingthe windings of the dilerent magnets with 'different conductors of apolypliase circuit, whereby the currents traversing said windings aredephased with respect to each other, and means for connecting themovable core elemlents pf the diferent .magnets with said control ever.

2. The combination with an elevator brake mechanism comprising a brakedrum, braking means co-acting therewith, and a` control lever, of aplurality of singlephase electromagnets each comprising a movable U-shaped plunger, a o o-acting stationary core element loosely mounted toeffect engagement with the ends of 'the limlbs of said U- shapedplunger, and an exciting winding, sai'd windings' traversed,respectively, by currents which are dephased with respect 'dephasedwithy respect to each other, and' means for connecting the movable coreelements of the different magnets independently of each other with saidcontrol lever. 4. The combination with an elevator brake mechanismcomprising a brake drum, braking means co-acting therewith, and acontrol lever, of a plurality of independent single phaseelectro-magnets whose magnetic circuits are substantially independentand each comprising relatively movable corey elements and awinding, thewindings of the different magnets traversed, respectively, by currentsdephased with respect to each other, means for connecting the movablecore elements of the ldifferent magnets independently of each other withsaid control lever, and means for effecting adjustment whereby themovable core elements come simultaneously into engagement with thestationary core elements. I

5. The combination with an elevator brake mechanism comfprising a brakedrum, braking means co-acting therewith, and a control lever, of aplurality of single phase electromagnets each comprising a movable U-shaped plunger, a co-actingv stationary core element loosely mounted toelect engagement with the ends of the limbs of said U- shaped plunger`and an exciting winding,

said windings traversed, respectively, by

currents which are dephased with respect to each other, means forconnecting said U- shaped plun ers with said control lever, and meansfor e ecting adjustment whereby said movable plungers comesimultaneously into engagement with their said stationary coreelelements.-

6. The combination with an elevator brake mechanism comprising a brakedrum, braking means co-acting therewith, a control` lever, and springmeans tending to move said braking means in a predetermined d1- rection,of a plurality of independent single phase electro-magnets eachcomiprising relatively movable core elements and a winding, the windingsof the different magnets traversed, respectively, by currents dephasedwith respect to each other, said core elements engaging each other at -arestricted area of magnitude suticie/nt to prevent chattering and lessthan the "area of the neighboring. faces of said core elements, and

means for connecting said vcore elements with said control lever tooppose said spring means upon energizationv of said magnets.v

7. The combination with an elevato-r brake mechanism comprising abrakedrum, braking means co-acting therewith, and a control lever, of asingle phase electro-magnet com-y prising an exciting Winding andrelatively movable core elements, oI'ie core element connected to' saidcontrol lever, and spring means opposing attractiony of said coreelements towards each other, said core ele'- ments engaging each other`in a restrictedv area materially less than the area of the opposingfaces of said ycore elements and sufficiently great -to preventseparation of said core elements under the influence? of said sp1-ingmleans at the intervals of zero magnitude of exciting alternatingcurrent.

8. The combination 4with an elevator brake mechanism comprising a brakedrum, braking means co-acting therewith, and a vcontrol lever, of analternating current electromagnet comprising an exciting Winding, a

relatively fixed co-re element, `a, movableshaped core elementvcci-'acting thereWith,

and means for loosely supporting said relatively fixed core element topermit it to eiect` accommodation With the ends of said U- l shaped coreelement,'and means vl'orrconnecting saidU-shaped core element withv'said controllever. 1 l I v 9. The combination with an elevator brakemechanism, of a plurality of single phase electro-magnets controllingsaid "brake mechanism, said electro-magnets having substantiallyindependent magnetic ci'rcuits, and each' comprising relatively mlovablecore elements -and a Winding, means connecting the-windings of thedifferent magnets with different phases of a polyphase circuit, wherebythe currents traversing saidw'indings are dephasedwith respect toeachother, and means for connectingthe movable core elements of thediHerent-magnets with said brake mechanism.

',WILLARD js'. ATKINSON.

